What does "takes an action" mean?

Question

The context of this question, is the following: I've recently joined a D&D table, which happened to be with only new players, including the DM himself.

The other day, our DM introduced us a new cool creature: Spawn of Kyuss (MotM, p. 225). This undead has an action that is called "Burrowing Worm", and this attack has the particularity of throwing a worm that sticks into the PC and deals damage. One of the conditions to remove the worm is "take an action", and that is where the nightmare begins for us (after the session).

Our characters are low-level enough for us not having a PC that has multiple attacks. But we were asking ourselves:

• What does take an action mean? Is it an attack? Is it an reaction? Is it the movement of the player? Is it a bonus action? Is it any of the previous categories?
• Under that reasoning: if any of us wants to scrape off the goddamed worm, will they lose their turn in combat?
• Then, we started wondering if a level 5th barbarian with his extra attack would be able to remove the worm and attack? And if that is the case: would he have lost the ability to relocate himself and possibly lost his extra attack as well?

The questions are so many, but our problem is simple: we do not understand what "take an action" means. Which would be the way to resolve that requirement? What would it cost a player?

Answer 1

There are five things that you can do in a round:

• Action
• Bonus Action
• Reaction
• Movement
• Interact with an Object

If something takes an action, that means that your Action is not available to use for other things. (The most common being the Attack Action, or Cast A Spell).

Answer 2

This is going to be a long answer: it recalls at the beginning the basic rules for the "action economy" in combat, then provides some examples and finally tries to clarify the case at hand.

Common rules for combat

The combat is divided in rounds, where the participants take turns following the initiative order.

Each participant, during a round, may do 4 things, which have specific names:

• Action
• Bonus Action
• Movement
• Reaction

Normally, each option of the above list can be chosen only once per round¹, in any order. You can see such list as your "portfolio" of 4 "slots" that you can spend in a round: once you spent an "Action slot", you cannot use another one until your next turn. Beside these 4 "slots", you can also do other things that do not "cost" anything: check the section Other Activity on Your Turn.

Each element of the above list is actually a set of options: let's focus on Actions.

The basic options for Action are Attack, Cast a Spell, Dash, Disengage, Dodge, Help, Hide, Ready, Search, Use an Object: when a participant is taking an action (or using an action) means that they are spending the "Action slot" and choosing one among those options. These are some of the choices, not all: there are other things that can be done spending an Action.

Monsters in combat

Before considering the case in the question, let's spend some words about how monsters can use their "portfolio" in combat.

Even monsters follow the same rules, i.e. they have the same 4 "slots" to spend in a round, and moreover their stat blocks present further options with the relative rules. For example, the Goblin Boss has the following ability:

Nimble Escape. The goblin can take the Disengage or Hide action as a bonus action on each of its turns.

This means that a Goblin Boss can spend its "Bonus Action slot" for taking the Hide action or Disengage action: for example, during their turn, they use their Action to Disengage from an enemy in melee combat, use their Movement to move away (without provoking opportunity attacks thanks to disengaging) and then use their Bonus Action to Hide.

Under the "Action" list of the Goblin Boss, one can read:

Multiattack. The goblin makes two attacks with its scimitar. The second attack has disadvantage.

This means that this monster can spend their Action to take the Multiattack action, i.e. choose as option for the "Action slot" of their portfolio the option Multiattack.

Finally, the Goblin Boss has also a personalized choice for the Reaction:

Redirect Attack. When a creature the goblin can see targets it with an attack, the goblin chooses another goblin within 5 feet of it. The two goblins swap places, and the chosen goblin becomes the target instead.

This means that beside the other options available for a Reaction, the Goblin can spend their "Reaction slot" of their portfolio and use the above ability.

Finally, your case

First of all, note that the Burrowing Worm ability of the Spawn of Kyuss costs an Action: this means that when using their Action (spending their "Action slot") the Spawn has to choose the Burrowing Worm ability or the Multiattack, they cannot use both of them in the same turn.

The description of Burrowing Worm reports (emphases mine):

The worm is a Tiny undead with AC 6, 1 hit point, a 2 (−4) in every ability score, and a speed of 1 foot. While on the target’s skin, the worm can be killed by normal means or scraped off using an action.

This means that a creature affected by such worm that wants to get rid off of the parasite has the following options:

• They can spend their Action to attack the worm: Attack is one of the option for the "action slot".
• They can spend their Action to scrap it off: hence the "Action slot" is spent and they cannot use it for hiding or disengaging, for example.

Consider now the barbarian: at 5th level they have the Extra Attack feature:

Beginning at 5th level, you can attack twice, instead of once, whenever you take the Attack action on your turn.

This means that a Barbarian can attack twice if they spend their "Action slot" for the Attack option. In the case at hand, since the description of the Burrowing worm says that it "can be killed by normal means", the Barbarian could have spent their Action slot to attack the worm, and then, due to the Extra Attack feature, they have still a further attack.

Note that if the Barbarian decide to use their Action slot to scrap off the worm, because they are using the Action slot to take the "scrap off" action and not the Attack action.

---

¹ There are special game feature that allow to overrule this, for example fighter's Action Surge ability.

Answer 3

Action Economy

Hey, lets see if I can assist ;)

1. What does take an action mean? Is it an attack? Is it an reaction? Is it the movement of the player? Is it a bonus action? Is it any of the previous categories?

Set moves in your PHB and DMG are "actions". Its a designation to split up the economy. Se an action in combat is: Attacking, Grappleing, Dodging, Disengaging & Dashing or casting some spells. You take that action to describe what you are doing.

Some creatures or spells have effect conditions like: You have to use your action to break free or wipe off the acid, douse the flame, break the grapple. If you think about it realistically, an action takes the most effort.

2. Under that reasoning: if any of us wants to scrape off the goddamed worm, will they lose their turn in combat?

Per this scenario yes, anything classed as an action (like that of attacking) is lost, even with extra attack. Extra attack requires you to take the attack action and you only have 1 action.

3. Then, we started wondering if a level 5th barbarian with his extra attack would be able to remove the worm and attack? And if that is the case: would he have lost the ability to relocate himself and possibly lost his extra attack as well?

Movement is not an action or bonus action, it has its own designation - movement. You always have Action, Bonus Action, Reaction & Movement in a turn of combat. Use them all or use just one, do what you can to survive.

I will add though, it may be advantageous for a raging barbaian to keep the worms attached until the end of combat, as per the rage condition.